A study on histological features of lepra reactions in patients attending the Dermatology Department of the Government Medical College, Calicut, Kerala, India

[[[ Objectives: ]]] 1. To study and compare the clinical and histological features of Type 1 and Type 2 lepra reactions. 2. To document the histological patterns of Type 1 and Type 2 lepra reactions observed in the study population. [[[ Design: ]]] Two year cross sectional study. Patients attending the outpatient department of our tertiary care hospital, during the 2 year study period with clinical evidence of Type 1 (T1R) or Type 2 (T2R) lepra reactions were included in this study after obtaining written informed consent. During this period 34 T1R patients and 14 T2R patients attended our hospital. Biopsies were taken from reacting skin lesions of all patients and histological features were studied. [[[ Results: ]]] Dermal or intragranuloma oedema was evident in 50% of T1R patients and all of them had clinically severe reactions. The T1R patients showed three different histological patterns–pgrading reactions, downgrading reactions and reactions without upgrading or downgrading. Among T2R patients 8/14 showed neutrophil infiltration histologically, 5/14 showed no histological evidence of neutrophil infiltration and only one patient had features of neutrphilic vasculitis. Dermal oedema was seen in 11/14 cases. [[[ Conclusions: ]]] Histology revealing dermal or intragranuloma oedema on a background of leprosy granuloma favours the diagnosis of lepra reaction. A careful analysis of subtle variations in the cells constituting the granuloma may aid in differentiating between upgrading T1R, downgrading T1R or T1R without upgrading or downgrading. Histology can also be useful in distinguishing T2R from T1R, in the absence of typical erythema nodosum leprosum (ENL) lesions. Neutrophils are the major inflammatory cells in the former where as lymphocytes or macrophages predominate in the latter. We recommend that histopathological analysis should form an integral part of the evaluation of all lepra reactions.